Combined permanent magnet and electromagnet assembly for thermoelectric safety devices



p 18, 1956 G. 1. HOLMES 2,763,277

COMBINED PERMANENT MAGNET AND ELECTROMAGNET ASSEMBLY FOR THERMOELECTRIC SAFETY DEVICES Filed Aug. 10, 1951 INVENTOR.

United States Patent COMBINED PERMANENT MAGNET AND ELEC- TROMAGNET ASSEMBLY FOR THERMOELEC- TRIC SAFETY DEVICES Gifford I. Holmes, Waukeslia, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis, a corporation of Wisconsin Application August 10, 1951, Serial N 0. 241,239

8 Claims. (Cl. 137-66) This invention relates, in general, to thermoelectric safety shut-off devices, and has particular relation to an improved combined permanent magnet and electromagnet assembly for such devices.

The present invention may be characterized in its more limited aspects as an improvement in devices having a magnet frame and coil assembly, in general, of the character disclosed and claimed in my copending application, Serial No. 241,23 8, filed August 10, 1951.

According to the invention of my above-mentioned copending application, there is provided an electromagnet comprising an improved magnet frame and coil assembly wherein the cross-sectional area of the magnet frame, the magnetic flux path, the diameter of the wire, and the number of turns of wire for the coil may all be reduced to a minimum. The magnet frame and coil assembly of that application also functions more efficiently since the base of the magnet frame around which the coil is wound may be saturated, or substantially saturated, with magnetic flux throughout its entire cross-sectional area and throughout its entire extent. tageous since they reduce the amount of special material required, and the size, weight, and cost of the magnet frame and coil assembly.

One of the main objects of the present invention is to enable further reduction of the size, weight, and cost of the magnet frame and coil, and to provide a device that will operate effectively for its intended purpose.

Another and more specific object of the invention is to provide a device wherein the controlling member is held in operating position by the combined magnetic attraction of a permanent magnet and an electromagnet energized by the heat of a flame on a thermoelectric generator as long as the thermoelectric generator is heated by the flame but with which, on extinguishment of the flame, the controlling member is moved to safety position by the release of the armature means from the electromagnet and the permanent magnet. This is advantageous in that it enables the use of an electromagnet, the magnetic attraction of which alone is insufficient to hold the controlling member in operating position, thereby enabling a further reduction in the amount of special material required in the magnet frame of the electro magnet, and enabling the cross-sectional area of the magnet frame, the magnetic flux path in the electromagnet, the diameter of the wire, and the number of turns of wire for the coil to be further reduced.

Another object of the invention is to provide a device of the class described wherein the armature means comprises a first armature for the electromagnet and a second armature for the permanent magnet, and wherein one of the armatures is adjustable to adjust the effectiveness of the combined magnetic attraction produced by the electromagnet and the permanent magnet.

The invention also includes certain features of construction and assembly, and certain combinations and arrangements of the several parts to provide a device which is These factors are advan- 2,763,277 Patented Sept. 18, 1956 relatively simple and inexpensive, and operates effectively for its intended purpose.

Further objects and advantages of the invention will appear from the following detailed description, taken in connection with the accompanying drawing.

In the drawing:

Figure l is a longitudinal axial section through a complete hood assembly containing a magnet frame and a coil assembly and permanent magnet embodying the. present invention, and showing more or less diagrammatically a thermoelectric generator in circuit with the coil wire and positioned where it will be heated by the flame of a pilot burner disposed in lighting proximity to a main burner;

Figure 2 is a transverse sectional view taken on the line 22 of Figure l; and

Figure 3 is a bottom plan view of the magnet frame of the electromagnet.

Referring now to the drawing, the burner shown at 1 is a main burner. It may be the main burner for a room or space heater, or it may be the burner for a water heater or for a floor furnace, an oven burner, one or more top burners for a gas range, or any other burner and of any suitable construction.

A fuel supply pipe or conduit 2 leads to the burner 1 for the delivery of gaseous or other fuel thereto; for example, through a mixing chamber 3 to which air is admitted through adjustable air inlets (not shown), as well understood in the art. The flow of gas through the conduit is in the direction indicated by the arrow 4, and is controlled by a valve member 5. It is to be understood that the controlling member, instead of being in the form of a valve member, may be in the form of an electric switch, or of other form. The valve member 5 is shown in full lines in open position away from its annular valve seat 6 at one end of a valve opening 7 formed, for example, in a partition within the valve body which is shown fragmentarily and diagrammatically at 8. Contiguous sections of the fuel supply pipe 2 are connected to the inlet 9 and outlet 10 of the valve body.

The pilot burner 11, which is located in juxtaposition to the main burner 1 to maintain a pilot flame for igniting the main burner, is supplied with gaseous fuel by a pilot supply pipe 12. The pilot fuel supply pipe 12 may be connected, for example, to the pipe 2 anterior of the valve member 5, or through the valve body, or to any other source of fuel supply. The positions of the pilot burner flames are shown in dotted lines for purposes of illustration.

The magnet frame, terminal bushing, terminal tip, and coil assembly selected for illustration are of the type more fully disclosed in my copending application previously identified herein, and comprise a generally U-shaped magnet frame 15. The magnet frame 15 is preferably formed of a special alloy which is non-corrosive and has a high degree of permeability with minimum retentivity. Although the present invention is in nowise limited thereto, Permalloy (which is an alloy composed of about nickel and 20% iron); and Alleghany 4750 (which is an alloy composed of about 50% nickel and 50% iron) are suitable alloys for the magnet frame 15. The use of Armco iron (which has characteristics somewhat similar to Swedish electrolytic iron and is substantially pure iron) and other irons is contemplated within the scope of the present invention.

The magnet frame 15 has an imperforate base 16 of minimum cross-section and legs 17 of minimum length extending from opposite ends of the base. Although the present invention is not limited to particular dimensions, the dimensions for a given strength structure may be less than those set forth as a specific example in my previously identified copending application. A coil 25 of wire of 3 minimum diameter and minimum number of turns is wound around the base 16 of the magnet frame. Further to illustrate one particularly satisfactory embodiment of the invention, the coil 25 for the magnet frame 15 may be formed of copper wire of less diameter and less length than set forth in my copending application.

A metallic or conducting terminal bushing 26 has an aperture 27 therethrough in register with an aperture 28 in the base 29 of a generally U-shaped supporting bracket 30. A tubular neck 31, integral with the bushing 26, extends through the aperture 28 and is spun over at 32 to secure the bracket 30 firmly to the bushing 26. The legs 33 of the bracket 30, which are shown as diverging slightly from the base 29, straddle the magnet frame 15 and have inturned ends 34 which engage (detachably, if desired) in recesses or transversely elongated slots 35 in the opposite ends of the magnet frame. The inner ends of the slots 35 may be of arcuate contour formed, for example, by cutting them with a circular cutter.

The magnet frame 15 is thus mounted without providing an aperture in the base 16 around which the coil is wound. This enables making the base 16 of minimum cross-section; also so that it will be effective as a magnetic flux path throughout its entire cross-section; and so that in the operation of the device the base 16 may be saturated, or substantially saturated, with magnetic flux throughout its entire cross-sectional area and throughout its entire extent.

With the coil 25 wound on the base 16, the legs 17 of the magnet frame may be of minimum length. This provides a magnetic flux path of minimum length and, with the other distinguishing features, reduces the size, weight, and cost of the magnet frame and coil assembly.

The outer end of the bushing 26 has a depression in which there is a terminal tin 36 of brass or other suitable conducting material. Packing or insulating sealing material 37 is interposed between and serves electrically to insulate the terminal tip 36 from the bushing 26. The material 37 is preferably formed of material which is resistant to gaseous hydrocarbons so as to form a gastight joint between the bushing 26 and the terminal tip 36.

One end of the coil wire 25 extends through the tubular neck 31 and out through a registering aperture in the terminal tip 36, and is welded at 38 to a conically raised surface on the terminal tip 36. The coil wire 25. is preferably insulated at 39 by a suitable insulating wrapping. An annular insulating packing ring 49 is positioned about the outer margin of the outer surface of the terminal tip 36, and an integral annular flange on the tip 36 is bent or spun over against the packing to provide gastight relation between the respective parts of the device. The ring 49 is also preferably formed of insulating material which is resistant to gaseous hydrocarbons.

A magnet hood or cup 45 is positioned over the magnet frame and coil assembly, and is spun at 46 into engagement with the terminal bushing 26. A stem 47 is mounted for reciprocatory movement through an opening formed by an eyelet 48 in the base of the cup 45. A first armature 50 is mounted for relative movement on the inner end of the stem 47 to permit selfeaccommodation to the pole faces at the ends of the legs 17 of the magnet frame; for example, by extending the reduced inner end of the stem 47 through an opening in the armature 50 and swaging the inner end of the stem at 51.

The valve disc is retained on the opposite end of the stem 47 by a retaining ring 52, and a coiled spring 53 is interposed between the valve disc 5 and a valve spring seat 54 between which and the adjacent end of the hood 45 packing or sealing material is interposed at 54 to provide a gas-tight seal. The valve disc gasket 5 is clamped against the valve disc part 55 by a valve disc screw 56 screwed on the valve disc part 55.

The thermoelectric generator 60 is shown in the form of a thermocouple having elements of different thermoelectric characteristics joined at 61 to form the hot junction. The thermoelectric generator may be in the form of a thermopile, or of any other suitable form. The hot junction 61 is disposed in the pilot burner flame, or where it will be heated by the flame of the pilot burner 11 as long as the pilot burner is ignited. One side of the thermoelectric generator is connected, for example, by a conductor 62 in circuit with the welded contact at 38 and thus to one side of the coil 25. The other side of the thermoelectric generator 60 is connected by a conductor 63 in circuit with the terminal bushing 26. The other side of the coil 25 is connected to the terminal bushing 26, for example, by a resistance weld at 64.

As shown in Figure 3, the legs 17 preferably extend laterally beyond the sides of the base 16 of the magnet frame 15. This provides expanded pole faces at the ends of the legs 17; also guides and retention for the coil 25, and it provides pole faces which are not saturated when the base 16 is saturated, or substantially saturated, with magnetic flux. This eliminates or reduces leakage at the pole faces.

A permanent magnet 68 of annular disc-like form is carried within the hood 45 and has an opening through which the stem 47 extends for reciprocatory movement. This opening is preferably faced by an eyelet 69 of brass or other lubricating or nongalling material. The magnet 68 need contain no critical materials, and is preferably a carbon steel or chrome carbon type of permanent magnet.

A second armature 70 is screwed at 71 on the stem 47 in position within the hood 45 for attracted relation to the permanent magnet 68 when the first armature Si) is in attracted relation to the pole faces of the magnet frame 15 of the electromagnet. When the armatures 50 and 75 are in their attracted positions as shown in Figure 1, and the electromagnet is energized by the heat of the pilot flame on the one or more hot junctions 61 of the thermoelectric generator 69, the combined magnetic attraction of the electromagnet and the permanent magnet holds the armatures 50 and 70 in their attracted positions and the valve or controlling member 5 in its open or operating position.

The magnetic attraction of the electromagnet and the permanent magnet 68, each alone however, is insufiicient to hold the armatures 50 and 70 in their attracted positions and the controlling member 5 in its operating position. Accordingly, on extinguishment of the flame of the pilot burner 11 the controlling member 5 is moved by the spring 53 to its closed or safety position to shut off the supply of fuel to the main burner 1, and also preferably to the pilot burner 11.

The effectiveness of the magnetic attraction of the permanent magnet 68 for the second armature 7i and thereby the effectiveness of the combined magnetic attraction produced by the electromagnet and the permanent magnet may be adjusted to any desired amount by the simple expedient of screwing the second armature 70 to different positions along the stem 47. In this way the device may be adjusted for different tensions in the spring 53 and to hold any desired load or a controlling member of any desired weight in operating position.

Where, upon energization of the electromagnet by the heat of the flame of the pilot burner on the hot junction or junctions of the thermoelectric generator, the combined magnetic attraction produced by the electromagnet and the permanent magnet is insufiicient to move the armatures 50 and 70 to their attracted positions and the controlling member 5 to its operating position, reset means (not shown) may be provided for resetting the device, as well understood in the art. One illustrative form of such reset means with flow interrupter means therefor is shown and described in Charles V. Hildebrecht Patent No. 2,114,446, patented April 19, 1938.

The cited example of an electromagnet embodying the present invention will exert substantially one and one-half pounds of force when the armature is engaged with the pole faces of the magnet frame.

With the armatures 50 and 70 thus reset to their attracted positions upon ignition of the pilot burner 11, the flame thereof, by heating the one or more hot junctions of the thermoelectric generator 60 energizes the electromagnet, and the combined magnetic attraction produced by the electromagnet and the permanent magnet holds the armatures 50 and '70 in their attracted positions and the valve or controlling member in open position.

If the pilot burner 11 is extinguished, or the circuit for the thermoelectric generator 60 is opened or disabled, the electromagnet ceases to hold the armatures 50 and 70 in their attracted positions. The valve 5 is thereupon closed against the valve seat 6, for example, by the spring 53 to shut off the flow of fuel to the main burner 1, and preferably also the flow of fuel to the pilot burner.

When the. electromagnet armature 50 moves to retracted position it may, if desired, move into the field of the permanent magnet 68. In such case the permanent magnet performs a dual function. It works (1) with the electromagnet to perform a function which either alone is incapable of performing, and (2) to attract the armature 50 in its movement to retracted position whereby to provide additional sealing force for the valve 5.

The embodiment of the invention shown in the drawing is for illustrative purposes only, and it is to be expressly understood that said drawing and the accompanying specification are not to be construed as a definition of the limits or scope of the invention, reference being had to the appended claims for that purpose.

I claim:

1. A thermoelectric control valve comprising, in combination, armature means having attracted and retracted positions, a valve member having a first position and a second position and connected to said armature means for movement to its first position only upon movement of the complete armature means to retracted position and to its second position only upon movement of the complete armature means to attracted position, magnetic means for holding said armature means in attracted position and said valve member in its second position, said magnetic means comprising a permanent magnet and an electromagnet each fixedly positioned and each coacting directly with said armature means, said electromagnet being energized by a thermoelectric generator, said permanent magnet presenting a holding action which augments theholding action of said electromagnet to hold the complete armature means in attracted position and said valve member in its second position with a combined holding action greater than the maximum holding action of said electromagnet as long as said electromagnet is energized, the holding action of said permanent magnet and said electromagnet each being insuiiicient alone to hold any portion of said armature means in attracted position or said valve member in its second position, and biasing means effective whenever said electromagnet is deenergized to actuate the complete armature means to retracted position and said. valve member to its first position, said permanent magnet being positioned between said electromagnet and said valve member and said armature means comprising a pair of connected armature portions one operable between said electromagnet and said permanent magnet for alternative magnetic cooperation therewith when said armature means is in attracted and retracted positions respectively, the other of said armature portions being operable between said permanent magnet and said valve member.

2. A thermoelectric control valve comprising, in combination, armature means having attracted and retracted positions, a valve member having a first position and a second position and connected to said armature means for movement to its first position only upon movement of the complete armature means to retracted position and to its second position only upon movement of the complete armature means to attracted position, magnetic means for holding said armature means in attracted position and said valve member in its second position, said magnetic means comprising an annular disc-shaped permanent magnet and an electromagnet each fixedly positioned and each coacting directly with said armature means, said electromagnet being energized by a thermoelectric generator, said permanent magnet presenting a holding action which augments the holding action of said electromagnet to hold the complete armature means in attracted position and said valve member in its second position with a combined holding action greater than the maximum holding action of said electromagnet as long as said electromagnet is energized, the holding action of said permanent magnet and said electromagnet each being insuflicient alone to hold any portion of said armature means in attracted position or said valve member in its second position, and biasing means effective whenever said electromagnet is deenergized to actuate the complete armature means to retracted position and said valve member to its first position, said permanent magnet being positioned between said electromagnet and said valve member and said armature means comprising a pair of connected armature portions one operable between said electromagnet and said permanent magnet for alternative magnetic cooperation therewith when said armature means is in attracted and retracted positions respectively, the other of said armature portions being operable between said permanent magnet and said valve member, the connection between said armature portions comprising a stem having reciprocatory movement through an opening in said permanent magnet and connected to said armature portions.

3. A thermoelectric control device for the control of fuel fiow comprising, in combination, armature means having attracted and retracted positions, a controlling member having a first position and a second position and connected to said armature means for movement to its first position only upon movement of the complete armature means to retracted position and to its second position only upon movement of the complete armature means to attracted position, magnetic means for holding said armature means in attracted position and said controlling member in its second position, said magnetic means comprising a permanent magnet and an electromagnet each fixedly positioned and each coacting directly with said armature means, said electromagnet being energized by a thermoelectric generator, said permanent magnet presenting a holding action which augments the holding action of said electromagnet to hold the complete armature means in attracted position and said controlling member in its second position with a combined holding action greater than the maximum holding action of said electromagnet as long as said electromagnet is energized, the holding action of said permanent magnet and said electromagnet each being insufficient alone to hold any portion of said armature means in attracted position or said controlling member in its second position, and biasing means effective whenever said electromagnet is deenergized to actuate the complete armature means to retracted position and said controlling member to its first position, said permanent magnet being positioned between said electromagnet and said controlling member and said armature means comprising a pair of connected armature portions one operable between said electromagnet and said permanent magnet for alternative magnetic cooperation therewith when said armature means is in attracted and retracted positions respectively, the other of said armature portions being operable between said permanent magnet and said controlling member, the connection between said armature portions comprising a stem having reciprocatory movement through an opening in said permanent magnet and connected to said armature portions, one of said armature portions being screwed on said stem for adjustment thereon to adjust the combined magnetic action of said electromagnet and said permanent magnet on said armature portions.

4. A thermoelectric control device comprising, in combination, an electromagnet frame of generally U-shaped form having an imperforate base of uniform cross-section and a pair of legs extending from the opposite ends of said base, the legs of the electromagnet frame extending laterally from the sides of the base to provide expanded pole faces at the ends of said legs, a first armature connected to one end of a movable armature stem for coaction with the pole faces of said electromagnet frame, a permanent magnet of annlar disc-like form having an opening through which said armature stem reciprocates, a second armature mounted on said armature stem and positioned in attracted position at said permanent magnet when said first armature is positioned at the pole faces of said electromagnet frame, means biasing the first and second armatures mounted upon said armature stem away from the pole faces of said electromaget frame and from said permanent magnet respectively; said biasing means providing a biasing force sufiicient to move said second armature away from attracted position at said permanent magnet, means providing a source of electrical energy of limited magnitude, a coil of wire wound around the base of said electromagnet frame between said legs and connected in circuit with said source of electrical energy, said coil composed of the minimum number of turns of wire of the minimum diameter necessary to create a magnetic flux through said electromagnet frame sufficient only to hold said first armature in attracted position at said pole faces and said second armature is in attracted position at said permanent magnet, the base of said electromagnet frame having a cross-sectional area large enough only to be substantially saturated by the magnetic flux induced by said coil.

5. A device according to claim 4 wherein the second armature is screwed upon the armature stem for adjustment along said stem to adjust the effectiveness of the combined magnetic attraction produced by said permanent magnet and the electromagnet provided by the electromagnet frame and coil assembly.

6. In a control device having a controlling member movable to flow permitting and flow preventing positions, the combination of armature means movable to attracted and retracted positions and connected to said controlling member for movement of said controlling member to flow permitting and flow preventing positions when said armature means moves to attracted and retracted positions respectively, magnetic means for holding said armature means in attracted position and said controlling member in flow permitting position, said magnetic means comprising a permanent magnet and an electromagnet each fixedly positioned and each coacting directly with said armature means, said permanent magnet providing a holding action which augments the holding action of said electromagnet to hold the complete armature means in attracted position and said controlling member in flow permitting position, the holding action of said permanent magnet and said electromagnet each being insulficient alone to hold any portion of said armature means in attracted position and said controlling member in flow permitting position, said armature means including an armature portion operable between said electromagnet and said permanent magnet for alternative magnetic cooperation therewith when said armature means is in attracted and retracted positions respectively to thereby aid in positioning said controlling member in each of its said flow-permitting and flow-preventing positions.

7. In a thermoelectric shut-off valve having a valve member biased to flow preventing position and movable to flow permitting position, the combination of armature means connected to said valve member and magnetic means for holding said armature means in attracted position and said valve member in flow permitting position, said magnetic means comprising an electromagnet connected in circuit with a thermoelectric generator and having a relatively weak magnetic holding action compared with the bias of said valve member to flow preventing position, and a permanent magnet of annular disc-like form providing a magnetic holding action which acts on said armature means in the same direction as said electromagnet, the resultant magnetic holding action of said electromagnet and the holding action of said permanent magnet each being insuificient alone to hold said valve member in open position so that said valve member will operate to closed position upon deenergization of said electromagnet, said armature means comprising a first armature operable between said electromagnet and said permanent magnet for alternative magnetic cooperation therewith when said armature means is in attracted and retracted positions respectively to thereby aid in positioning said valve member in each of its said flow-permitting and flow-preventing positions and a second armature for the permanent magnet, each of said first and second armatures being mounted upon a single reciprocatory armature stem, said stem having reciprocatory movement through an opening in the permanent magnet and being connected to said valve memher.

8. A thermoelectric shut-off valve according to claim 7 wherein the electromagnet comprises a magnet frame of generally U-shaped form having an irnperfora'te base of uniform cross-section and adapted to be substantially saturated with magnetic flux throughout its entire crosssectional area and throughout its entire extent, said magnet frame having legs extending from the opposite ends of said base, and a coil of wire wound around the base of said magnet frame.

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